Boats powered by an inboard style propulsion system typically feature a multi-part driveline consisting of: (1) a motor or engine with a driving shaft or power takeoff, (2) amounting apparatus for the motor or engine, (3) a propeller shaft coupled to the driving shaft of the motor/engine and passing through the bottom of the boat's hull, (4) a packing box or stuffing box, or shaft log and shaft seal, which fastened to the inside hull bottom and through which the propeller shaft exits the hull and enters the water (5) a strut and bearing assembly, which protrudes downward from the exterior hull bottom and through which the propeller shaft passes such that the strut and bearing provide support and rigidity to the shaft beneath the hull, (6) a propeller, which is mechanically fastened to the end of the propeller shaft, and (7) a rudder, which extends below the hull bottom to direct the forces of the propeller, but which has a vertical stem that passes up, through and into the hull inside of a rudder bearing tube which is attached to the boat's hull bottom. Collectively, these seven components (motor, motor mount, shaft, shaft log, strut, propeller, and rudder) integrate to transmit and direct the motive forces of the inboard power plant. The effectiveness of such an inboard drive line is sensitive to the accurate alignment of the components relative to one another.
In traditional inboard drive line configurations, the installation of motor, motor mount, propeller shaft, and shaft log occur within the interior of the hull cavity, whereas the position and alignment of the strut, propeller, and rudder are set beneath the hull's exterior bottom. Because these interdependent installations occur on opposing sides of the hull's bottom, it can be very challenging to properly coordinate and align all components. Additional time and/or workers can be required to achieve a proper alignment of all components. An improper or imprecise alignment can cause problems such as friction or vibration during operation. The process is further complicated because the surface topology of a hull's interior may be inconsistent or irregular due to inexactness in fiberglass laminations or other construction methods used to fabricate the hull.
What is needed is a single, uniform mounting plate structure, shared by all the driveline components, and which a single technician can easily reach above and below when pre-aligning the integration of driveline components.